test: reorganize fixture files into modality-first layout (phase 6b)

Move all fixture files from flat/mixed dirs (content/, media/, documents/,
formats/, hostile/, root loose) into the modality-first hierarchy:
image/{valid,formats,edge,hostile}, video/{valid,formats,hostile},
audio/{valid,formats,hostile}, document/{valid,formats,edge,hostile},
data/valid/, security/. Update index.ts paths, fixtureDir aliases,
all literal refs in 17 e2e/qa/script files, manifest.json, and the
three generator scripts. 163 files moved, 0 dropped, 100 new tests
from expanded document scan.

tests/e2e/state-bleed-audit.spec.ts

@@ -133,7 +133,14 @@ test.describe("State bleed between tools", () => {
       await addMoreBtn.click();
       const fileChooser = await fileChooserPromise;
       await fileChooser.setFiles(
-        require("node:path").join(process.cwd(), "tests", "fixtures", "test-50x50.webp"),
+        require("node:path").join(
+          process.cwd(),
+          "tests",
+          "fixtures",
+          "image",
+          "valid",
+          "test-50x50.webp",
+        ),
       );
       await page.waitForTimeout(500);
     }